Enabled 'dense' mode for Table cells.

Hardcoded cell styling for Table was removed to enable 'dense' as a cell padding choice.
Padding customisation for inherited smallSize was added.
Dense mode was chosen for sentry issues table rows.

packages/theme/src/baseTheme.ts

@@ -118,9 +118,12 @@ export function createThemeOverrides(theme: BackstageTheme): Overrides {
         verticalAlign: 'middle',
         lineHeight: '1',
         margin: 0,
-        padding: '8px',
+        padding: theme.spacing(3, 2, 3, 2.5),
         borderBottom: 0,
       },
+      sizeSmall: {
+        padding: theme.spacing(1, 2, 1, 2.5),
+      },
       head: {
         wordBreak: 'break-word',
         overflow: 'hidden',